1. Field of the Invention
The present invention relates generally to a safety device for motor-operated doors such as, for example, segmented doors or rolling shutter doors. The safety device is used to sense an object located in the movement path of a door, rolling grille, lift away shutter door and the like.
1. Description of the Related Art
Such safety systems are known, for example, from the documents DE-U-8615042 or DE-A-3416546. According to DE-U-8615042, a safety strip, composed of a tube made of elastomeric material, of a termination profile is provided on one side with a lamp and on the other side with a light-sensitive resistance element. If the safety strip strikes an obstacle, the light beam is interrupted, causing a switching pulse which activates the engine brake to be generated.
DE-A-3416546 relates to a safety device for stopping motor-driven objects. In order to bring about improved response of the safety device for stopping motor-driven objects having a photoelectric barrier arrangement, the photoelectric barrier arrangement is composed of a light transmitter and a light receiver which are arranged at the two ends of a profiled rail having a light duct. When an obstacle is struck, the profiled rail composed of an elastically deformable material is squeezed together, causing the cross-section of the light duct to be reduced, so that the light beam is interrupted.
However, in these elastically deformable safety strips, adequate protection against injuries and damage is provided only if their deformation range corresponds to the follow-on travel of the leading edge of the terminating profile from the activation of the switching device up to the point where it is braked to a complete standstill. Owing to the weight, and in particular the kinetic energy, of the door leaf and of the terminating profile, there is, apart from the switching deceleration, a relatively long follow-on travel so that high, and thus expensive, safety strips have to be used.
A further disadvantage of such safety strips comprising profiled elastomeric material is, in addition to the unavoidable activation force and the resistance force resulting from its deformation, the fact that switching decelerations, or even switching failures, may occur depending on the direction of impact.
Owing to these problems, the procedure of arranging photoelectric barrier arrangements at a distance corresponding at least to the follow-on travel of the door leaf, in front of the leading edge of the terminating profile of the leaf door, so that the movement of the door leaf is stopped if an obstacle interrupts the light beam of the photoelectric barrier arrangement. Since the light beam runs at a distance in front of the terminating profile of the door leaf, it is ensured that the terminating profile does not come into contact with an obstacle which interrupts the light beam.
Examples of this are given in the documents EP-B-0325602 and EP-B-0284066. EP-B-0325602 discloses a safety device for rolling shutter doors in which the switching device is composed of a photoelectric barrier whose transmitter and pickup elements are arranged on each side of the terminating profile underneath said profile on supporting arms, at a distance corresponding to the braking distance. The supporting arms are guided in a sliding fashion in respective securing elements which are connected to a lower part of the door leaf. If the supporting arm strikes against the ground or a stop, the transmitter and pickup elements are displaced relative to the door leaf and toward it and arrive, at the end of the closing movement of the door, at a position which lies at least at the level of the lower terminating edge of the door leaf.
EP-B-0284066 discloses a high-speed door with a switching device which is provided in the region of the lower edge of the terminating profile and allows the brake to engage when said switching device is activated. The switching device is composed of a photoelectric barrier whose transmitter and sensor element are arranged on each side of the terminating profile at a distance below it corresponding to the braking distance, in the region of the lower ends of plungers which are guided so as to be capable of insertion in guides on the terminating profile or lateral blade-like projections. When the plungers strike the ground or a stop, the plungers dip into the guides so that the terminating profile can be supported on the ground.
In the two examples mentioned above, the transmitter and sensor element are arranged on part of the door leaf, with the result that the transmitter and sensor elements are moved with the door leaf. Owing to this movement, the electrical leads and other components of the electric circuit which extend between the door leaf and frame are subject to strong dynamic loads which are caused by vibrations in the door leaf and continuous bending stresses. In addition, dirt, dust and water may become deposited on various electrical system components and lead to a decrease in the performance or a malfunction of the system. In many cases, the fact that the electrical supply of the sensor and transmitter element has to be led through the door, so that the design of the door or of the door segments has to be adapted to this, proves problematic in these known systems. This adversely affects the flexibility of the user, but also of the manufacturer, as far as the door design is concerned.
Photoelectric area sensor systems are also known for protecting doors, said sensors being mounted either on one side of the door leaf or else, in order to improve the protection, on both sides of the door leaf. In the first case, adequate protection of persons and property is not provided on the side of the door leaf which is not equipped with the area sensor. In the latter case, the expenditure is too high and the photoelectric area sensor system is too expensive. In addition, it is a common feature of both systems that they are susceptible to incorrect switching if, for example, power supply components such as, for example, coiled cables, dip into the beam path of the photoelectric area sensor in an uncontrolled fashion due to external weather influences or the door leaf itself bulges out when subjected to the wind.